U.S. patent number 11,281,187 [Application Number 16/660,710] was granted by the patent office on 2022-03-22 for numerical controller.
This patent grant is currently assigned to FANUC CORPORATION. The grantee listed for this patent is FANUC CORPORATION. Invention is credited to Chikara Tango, Daisuke Uenishi.
United States Patent |
11,281,187 |
Uenishi , et al. |
March 22, 2022 |
Numerical controller
Abstract
To provide a numerical controller that can detect a position in
a machining program at which a speed control abnormality is likely
to occur due to an insufficient look-ahead blocks that are used to
determine an acceleration/deceleration operation, and supplement
the look-ahead blocks at that position in order to stabilize feed
rate, cutting speed and other factors. A numerical controller
includes a required look-ahead blocks setting unit that sets a
required look-ahead blocks, which is a look-ahead blocks required
to execute a machining program, and an operation limitation unit
that compares a look-ahead blocks calculated by a look-ahead blocks
calculation unit to the required look-ahead blocks and, if the
look-ahead blocks is less than the required look-ahead blocks,
limits execution of the machining program until the look-ahead
blocks reach the required look-ahead blocks.
Inventors: |
Uenishi; Daisuke (Yamanashi,
JP), Tango; Chikara (Yamanashi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
FANUC CORPORATION |
Yamanashi |
N/A |
JP |
|
|
Assignee: |
FANUC CORPORATION (Yamanashi,
JP)
|
Family
ID: |
70326616 |
Appl.
No.: |
16/660,710 |
Filed: |
October 22, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200133240 A1 |
Apr 30, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 31, 2018 [JP] |
|
|
JP2018-205701 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B
19/416 (20130101); G05B 19/4142 (20130101); G05B
19/4155 (20130101); G05B 2219/42173 (20130101); G05B
2219/43009 (20130101); G05B 2219/35293 (20130101); G05B
2219/35386 (20130101) |
Current International
Class: |
G05B
19/4155 (20060101); G05B 19/414 (20060101); G05B
19/416 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Jarrett; Ryan A
Attorney, Agent or Firm: Studebaker & Brackett PC
Claims
What is claimed is:
1. A numerical controller for controlling a machine tool that has
axes by executing a machining program that is made up of a
plurality of blocks and controls acceleration/deceleration of the
axes, the numerical controller comprising: a program execution unit
that executes the machining program; a program look-ahead unit that
looks ahead at the machining program in parallel with execution of
the machining program; a look-ahead blocks calculation unit that
calculates a look-ahead blocks, which is the difference between a
first sequence number that is the number of a block being executed
by the program execution unit and a second sequence number that is
the number of a block that is looked ahead by the program
look-ahead unit while the machining program is being executed; a
required look-ahead blocks setting unit that sets a required
look-ahead blocks, which is the look-ahead blocks required to
execute the machining program; and an operation limitation unit
that compares the look-ahead blocks calculated by the look-ahead
blocks calculation unit and the required look-ahead blocks and, if
the look-ahead blocks is less than the required look-ahead blocks,
limits execution of the machining program by the program execution
unit until the look-ahead blocks reaches the required look-ahead
blocks.
2. The numerical controller according to claim 1, further
comprising a storage unit that stores blocks that are looked ahead
by the program look-ahead unit, where the stored blocks are
consumed by the program execution unit, wherein the required
look-ahead blocks setting unit sets the required look-ahead blocks
on the basis of maximum capacity of the storage unit.
3. The numerical controller according to claim 1, further
comprising a storage unit that stores the required look-ahead
blocks, wherein the required look-ahead blocks setting unit sets
the required look-ahead blocks using the required look-ahead blocks
stored the storage unit.
4. The numerical controller according to claim 1, wherein the
required look-ahead blocks setting unit sets the required
look-ahead blocks on the basis of a variable that is written in the
machining program together with a predetermined first code.
5. The numerical controller according to claim 1, wherein, the
machining program contains an iteration of a second code that
corresponds to identical machining, the numerical controller
further comprising a storage unit that stores a number of consumed
blocks that is the look-ahead blocks consumed when the second code
was previously executed by the program execution unit, and the
required look-ahead blocks setting unit setting, as the required
look-ahead blocks, a value in which the number of consumed blocks
is added to the look-ahead blocks before the code is executed when
the code is executed next or for subsequent times by the program
execution unit.
6. The numerical controller according to claim 1, wherein the
operation limitation unit instructs the program execution unit to
stop executing the machining program.
7. The numerical controller according to claim 1, wherein the
operation limitation unit reduces operation speed of the machine
tool specified in the machining program.
8. The numerical controller according to claim 1, further
comprising a supplement code addition unit that detects a block in
the machining program at which the look-ahead blocks calculated by
the look-ahead blocks calculation unit falls below a prescribed
value when a simulation of the machining program is executed, and
inserts a predetermined third code in the block, wherein, when the
third code is detected, the operation limitation unit compares the
look-ahead blocks and the required look-ahead blocks.
Description
This application is based on and claims the benefit of priority
from Japanese Patent Application No. 2018-205701, filed on 31 Oct.
2018, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a numerical controller.
Related Art
In the manufacturing industry today, IT parts and other devices are
being manufactured on smaller scales and with higher precision, and
interest in high-speed and high-precision machining is on the
rise.
In order to achieve even higher quality in machining, there has
been an increase in the number of workpiece machining programs for
high-speed and high-precision machining that are created with
tolerances on smaller orders.
Conventionally, machining programs with small tolerances could not
realistically be used due to low computer processing power.
However, in recent years, both computer performance and computer
aided manufacturing (CAM) performance have improved to the point
where machining programs with small tolerances can now be easily
created, and this trend is expected to grow in years to come
One aspect other than tolerance that is important when producing
high-quality machining is uniformizing minute straight lines.
Machining quality is increased when vibration is reduced through
stabilizing acceleration/deceleration at each axle. As a result,
there has been an increase in the number of high-quality machining
programs featuring even minute straight lines.
Therefore, machining programs are now made up of more blocks.
In the prior art, a numerical controller looks ahead at programs
and reads out and processes a program for blocks to be executed
next according to the first in, first out (FIFO) method from a
number of programs stored in advance equal to look-ahead blocks.
Then, the numerical controller determines an
acceleration/deceleration operation and performs axis control.
However, such high-quality machining programs have the following
problem.
That is, the programs have short minute straight lines and fast
command speed which means that, if the processing time for
executing the program is shorter than the time required for
look-ahead processing, the look-ahead blocks used to determine the
acceleration/deceleration operation cannot be secured. As a result,
acceleration/deceleration is not determined in consideration of
program behavior and changes in speed are not constant and
high-quality machining cannot be achieved.
FIG. 8 is a graph showing the difference in
acceleration/deceleration over time when change in speed is
unstable.
As illustrated in FIG. 8, speed initially moves stably at a command
speed of 6,000 mm/min. At 2,000 mm/min, there was insufficient
processing time for executing the program and the look-ahead blocks
used to determine the acceleration/deceleration operation could not
be secured. Therefore, speed became unstable and moved slightly as
indicated by the arrows in FIG. 8.
Such behavior is particularly significant when a machine tool has a
large number of axes, such as in 5-axis machining, and the
processing power of the numerical controller is decreased. These
problems can be solved by increasing the processing power of the
numerical controller used for looking ahead or executing machining
programs. However, similar problems occur when command speed is
further increased by making programs more detailed or updating
machines.
In particular, one example of a detailed machining program is
machining for impeller machining, which is a type of simultaneous
5-axis machining that is used for high-speed and high-quality
machining.
FIG. 9 illustrates an impeller 80 as an example of an impeller.
When the impeller 80 is machined, the hub surface 81 and the fillet
surface 82 need to be finished by machining at a fast feed rate
while using short minute straight lines. In addition, this
machining employs a smoothing function that places more processing
load on the CPU.
As shown in FIG. 10 which illustrates an example of impeller
machining, particularly when machining blades such as the main
blade (long blade) 83 and the splitter blade (short blade) 84, the
look-ahead blocks at the start of machining or partway through
machining may become zero and speed control may become
unstable.
In order to provide a solution to these problems, the invention
described in Patent Document 1 discloses a technology in which a
numerical controller monitors the amount of data in a buffer that
is held by the FIFO method until analysis data consisting of
analyzed NC data is used as acceleration/deceleration interpolation
means. In particular, the technology determines that there is
insufficient data when the amount of data predicted to exist in the
buffer falls below a lower limit threshold value.
Patent Document 1: Japanese Patent No. 3723015
SUMMARY OF THE INVENTION
However, the technology disclosed in Patent Document 1 only
increases the priority of the NC data analysis processing task when
it is determined that there is insufficient data and does not
determine what data in the NC data is insufficient or at which
position there is insufficient data, and is therefore unable to
deal with speed control abnormalities at places where data is
insufficient.
It is an object of the present invention to provide a numerical
controller that can detect a position in a machining program at
which a speed control abnormality is likely to occur due to an
insufficient look-ahead blocks that are used to determine an
acceleration/deceleration operation, and supplement the look-ahead
blocks at that position in order to stabilize feed rate, cutting
speed and other factors.
(1) A numerical controller according to the present invention is a
numerical controller (for example, a "numerical controller 100" to
be described later) for controlling a machine tool (for example, a
"machine tool 200" to be described later) that has axes by
executing a machining program that is made up of a plurality of
blocks and controls acceleration/deceleration of the axes, the
numerical controller including: a program execution unit (for
example, a "program execution unit 111" to be described later) that
executes the machining program; a program look-ahead unit (for
example, a "program look-ahead unit 112" to be described later)
that looks ahead at the machining program in parallel with
execution of the machining program; a look-ahead blocks calculation
unit (for example, a "look-ahead blocks calculation unit 113" to be
described later) that calculates a look-ahead blocks, which is the
difference between a first sequence number that is the number of a
block being executed by the program execution unit and a second
sequence number that is the number of a block that is looked ahead
by the program look-ahead unit while the machining program is being
executed; a required look-ahead blocks setting unit (for example, a
"required look-ahead blocks setting unit 114" to be described
later) that sets a required look-ahead blocks, which is the
look-ahead blocks required to execute the machining program; and an
operation limitation unit (for example, an "operation limitation
unit 116" to be described later) that compares the look-ahead
blocks calculated by the look-ahead blocks calculation unit and the
required look-ahead blocks and, if the look-ahead blocks is less
than the required look-ahead blocks, limits execution of the
machining program by the program execution unit until the
look-ahead blocks reaches the required look-ahead blocks.
(2) The numerical controller described in Item (1) may further
include a storage unit (for example, a "RAM 13" to be described
later) that stores blocks that are looked ahead by the program
look-ahead unit, where the stored blocks are consumed by executing
the program, in which the required look-ahead blocks setting unit
may set the required look-ahead blocks on the basis of maximum
capacity of the storage unit.
(3) The numerical controller described in Item (1) may further
include a storage unit that stores the required look-ahead blocks,
in which the required look-ahead blocks setting unit may set the
required look-ahead blocks using the required look-ahead blocks
stored in the storage unit.
(4) In the numerical controller described in Item (1), the required
look-ahead blocks setting unit may set the required look-ahead
blocks on the basis of a variable that is written in the machining
program together with a predetermined first code.
(5) In the numerical controller described in Item (1), the
machining program may contain an iteration of a second code that
corresponds to identical machining, the numerical controller may
further include a storage unit that stores a number of consumed
blocks that is the look-ahead blocks consumed when the second code
was previously executed by the program execution unit, and the
required look-ahead blocks setting unit may set, as the required
look-ahead blocks, a value in which the number of consumed blocks
is added to the look-ahead blocks before the code is executed when
the code is executed next or for subsequent times by the program
execution unit.
(6) In the numerical controller described in any one of Items (1)
to (5), the operation limitation unit may instruct the program
execution unit to stop executing the machining program.
(7) In the numerical controller described in any one of Items (1)
to (5), the operation limitation unit may reduce operation speed of
the machine tool specified in the machining program.
(8) The numerical controller described in any of the Items (1) to
(7) may further include a supplement code addition unit that
detects a block in the machining program at which the look-ahead
blocks calculated by the look-ahead blocks calculation unit falls
below a prescribed value when a simulation of the machining program
is executed, and inserts a predetermined third code is the block,
and, when the third code is detected, the operation limitation unit
may compare the look-ahead blocks and the required look-ahead
blocks.
According to the present invention, it is possible to detect a
position in a machining program at which a speed control
abnormality is likely to occur due to an insufficient look-ahead
blocks that are used to determine an acceleration/deceleration
operation, and supplement the look-ahead blocks at that position in
order to stabilize feed rate, cutting speed and other factors.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram for illustrating the configuration of a control
system including a numerical controller according to a first
embodiment of the present invention.
FIG. 2 is a diagram for illustrating the configuration of the
numerical controller according to the embodiment of the present
invention.
FIG. 3 is a diagram for illustrating function blocks for the
numerical controller according to the embodiment of the present
invention.
FIG. 4 is a diagram for illustrating an exemplary machining program
that is used in the embodiment of the present invention.
FIG. 5 is a graph for showing difference in the look-ahead blocks
according to the embodiment of the present invention over time.
FIG. 6 is a graph for showing difference in the look-ahead blocks
according to the embodiment of the present invention over time.
FIG. 7 is a flowchart for illustrating operation of the numerical
controller according to the embodiment of the present
invention.
FIG. 8 is a graph for showing instability of speed due to inability
to secure the look-ahead blocks.
FIG. 9 is a diagram for illustrating an exemplary impeller
configuration.
FIG. 10 is a graph for showing difference in the look-ahead blocks
over time in the prior art.
DETAILED DESCRIPTION OF THE INVENTION
Now, an embodiment of the present invention is described with
reference to FIGS. 1 to 7.
1. Outline of Invention
A look-ahead blocks becomes zero when the position of a block to be
looked ahead or the position of a block to be executed by a program
execution unit reaches the end of a machining program.
However, the look-ahead blocks usually does not evenly decrease to
zero. The rate reduction of look-ahead blocks changes depending on
the processing time for each block, which differs due to a change
in the curvature of the machining path or the axis
configuration.
For example, at a portion in the machining program where minute
straight lines are continuous with each other, the execution speed
of the machining program becomes slower and the processing time of
each block becomes shorter. When this happens, the look-ahead
blocks decrease at a higher rate of reduction.
In this case, the look-ahead blocks that are used to determine the
acceleration/deceleration operation cannot be secured and a speed
control abnormality occurs in which change in speed is no longer
constant.
As a result, in this embodiment, the actual look-ahead blocks is
compared with a required look-ahead blocks. If the actual
look-ahead blocks is insufficient, operation speed of the machine
tool becomes slower and execution of the machining may stop at a
block at which a speed control abnormality is expected to likely
occur.
During this time, the machining program continues to be looked
ahead and the look-ahead blocks is supplemented. With this
configuration, the required look-ahead blocks can be secured and a
speed control abnormality is less likely to occur.
2. Configuration of Invention
FIG. 1 illustrates the configuration of a control system 10 that
includes a numerical controller 100 according to a first embodiment
of the present invention and a machine tool 200 that is controlled
by the numerical controller 100.
The numerical controller 100 is a machine that outputs an operation
command to the machine tool 200 to numerically control the machine
tool 200 using functions to be described later.
A detailed description of the configuration and functions of the
numerical controller 100 is provided later.
The machine tool 200 is a device that performs predetermined
machining such as cutting.
The machine tool 200 includes a motor that is driven to machine
workpiece and a spindle and a feed axis that are attached to the
motor. The machine tool 200 also includes fixtures and tools that
correspond to the respective axes. The motor of the machine tool
200 is driven on the basis of an operation command that is output
from the numerical controller 100 such that the machine tool 200
performs predetermined machining.
Herein, the contents of the predetermined machining are not
particularly limited and types of machining other than cutting,
such as grinding, polishing, rolling or forging, may also be
employed.
FIG. 2 illustrates an exemplary configuration of the numerical
controller 100 according to the embodiment of the present
invention.
The numerical controller 100 primarily includes a CPU 11, a ROM 12,
a RAM 13, a CMOS 14, interfaces 15, 18 and 19, a programmable
machine controller (PMC) 16, an I/O unit 17, axis control circuits
30 to 34, servo amplifiers 40 to 44, a spindle control circuit 60,
and a spindle amplifier 61.
The CPU 11 is a processor that controls the entire numerical
controller 100.
The CPU 11 reads out a system program that is stored in the ROM 12
via a bus 25 and controls the entire numerical controller 100
according to the system program.
The RAM 13 stores temporary calculation data and display data and
various types of data that is input by an operator using a
display/MDI unit 70.
The CMOS memory 14 is a non-volatile memory that is backed up by a
battery (not shown) and that retains its storage state even when
power to the numerical controller 100 is turned off. The CMOS
memory 14 stores a machining program that was read to the CMOS
memory 14 via the interface 15, a machining program that was input
to the CMOS memory 14 via the display/MDI unit 70, and other
data.
The ROM 12 is pre-written with various types of system programs for
executing processing for an edit mode required to create and edit
machining programs and processing for automatic operation.
Various types of machining programs such as the machining programs
for implementing the present invention can be input using the
interface 15 or the display/MDI unit 70 and stored in the CMOS
memory 14.
The interface 15 can connect the numerical controller 100 to an
external device 72 such as an adaptor.
Machining programs, various parameters and other data are read from
the external device 72 side.
Machining programs that are edited within the numerical controller
100 can be stored in external storage means using the external
device 72.
The programmable machine controller (PMC) 16 outputs signals via
the I/O unit 17 to an auxiliary device (for example, an actuator in
the form of a robot hand used for replacing tools) for a machine
tool using a sequence program stored in the numerical controller
100 and controls the device.
The PMC 16 receives signals such as those for various switches on
an operation panel provided in the body of the machine tool, and
transmits those signals to the CPU 11 after executing required
signal processing.
The display/MDI unit 70 is a manual data input device that includes
components such as a display and a keyboard. The interface 18
receives commands and data from a keyboard in the display/MDI unit
70 and transfers those commands and data to the CPU 11.
The interface 19 is connected to an operation panel 71. The
operation panel 71 includes a manual pulse generator.
The axis control circuits 30 to 34 for each axis receive movement
command amounts for each axis from the CPU 11 and output the
commands for each axis to the servo amplifiers 40 to 44.
The servo amplifiers 40 to 44 receive these commands and drive
servo motors 50 to 54 for each axis.
Each servo motor 50 to 54 for each axis includes a position/speed
detector. The position/speed detectors output position/speed
feedback signals that are fed back to each axis control circuit 30
to 31 to perform feedback control for position/speed.
Note that this position/speed feedback is omitted from the block
diagrams.
The spindle control circuit 60 receives a spindle rotation command
for the machine tool and outputs a spindle speed signal to the
spindle amplifier 61.
The spindle amplifier 61 receives the spindle speed signal and
rotates the spindle motor 62 of the machine tool at the commanded
rotational speed to drive the tool.
The spindle motor 62 is connected to a pulse encoder 63 by a gear,
a belt, or another component.
The pulse encoder 63 outputs a feedback pulse in synchronization
with rotation of the spindle.
The feedback pulse is read by the CPU 11 via the bus 25.
In the exemplary configuration of the numerical controller 100
illustrated in FIG. 2, five axis control circuits (axis control
circuits 30 to 34) and five servo motors (servo motors 50 to 54)
are illustrated.
However, the present invention is not limited to this configuration
and any number of axis control circuits and servo motors may be
provided.
FIG. 3 is a function block diagram for illustrating a function
where the CPU 11 reads out system programs and application programs
stored in the ROM 12 via the bus 25 and implements the present
invention according to those system programs and application
programs.
The CPU 11 includes a program execution unit 111, a program
look-ahead unit 112, a look-ahead blocks calculation unit 113, a
required look-ahead blocks setting unit 114, a supplement code
detection unit 115 and an operation limitation unit 116.
The program execution unit 111 executes a machining program.
More specifically, in this embodiment, the program execution unit
111 executes a simulation of the machining program. During this
simulation, it is preferable, for example, that workpiece be placed
on the machine tool 200 and the machine tool 200 be actually
operated, instead of just executing the machining program idly.
This is because the difference in look-ahead blocks over time (to
be described later) changes depending on the operating environment,
and the axis configuration of the machine tool 200.
In parallel with the simulation of the machining program executed
by the program execution unit 111, the program look-ahead unit 112
looks ahead at the machining program before the simulation is
executed.
The look-ahead blocks calculation unit 113 calculates the
look-ahead blocks. This number is the difference between a first
sequence number of a block that is being executed by the program
execution unit 111 and a second sequence number of a block that is
looked ahead by the program look-ahead unit 112 at the time when
the first block is being executed.
The required look-ahead blocks setting unit 114 sets a "required
look-ahead blocks", which is the look-ahead blocks required to
execute the machining program.
The required look-ahead blocks setting unit 114 may set a single
"required look-ahead blocks" for one entire machining program or
may set a "required look-ahead blocks" for each block that makes up
a machining program, that is, each process of machining in a
machining program.
The required look-ahead blocks setting unit 114 may also set the
"required look-ahead blocks" on the basis of the maximum capacity
of a memory in which the look-ahead blocks are stored and executed
and consumed by the program execution unit 111.
The memory used in this case may be the above-described RAM 13 or
may be a storage device such as a buffer that is externally mounted
to the numerical controller 100.
Alternatively, the required look-ahead blocks setting unit 114 may
set, when each machining program is executed, the "required
look-ahead blocks" using a required look-ahead blocks that is
stored in the memory.
For example, the numerical controller 100 may store a table for
setting correspondence between an identifier for each machining
program and the "required look-ahead blocks" set for each machining
program. Then, the required look-ahead blocks setting unit 114 may
read the "required look-ahead blocks" that corresponds to the
machining program to be executed from the table.
Alternatively, as described later, a look-ahead block supplement
code may be inserted into the machining program and a user may
write this look-ahead block supplement code into the machining
program together with a variable. Then, the required look-ahead
blocks setting unit 114 may set the value set as the variable on
the basis of input from an input device of the numerical controller
100 or a value read for the variable from another subroutine as the
"required look-ahead blocks".
(In this embodiment, the "look-ahead block supplement code" is also
referred to as a "first code".)
Alternatively, if the machining program contains an iteration of a
code that corresponds to identical machining, the look-ahead blocks
consumed when the program execution unit 111 executed the code
previously may be stored in the memory as a "number of consumed
blocks" and, when the code is executed next and for subsequent
times, the required look-ahead blocks setting unit 114 may set a
value in which the "number of consumed blocks" has been added to
the look-ahead blocks before executing the code as the "required
look-ahead blocks".
(In this embodiment, a code that corresponds to identical machining
is also referred to as a "second code".)
The supplement code detection unit 115 detects the "look-ahead
block supplement code" inserted into the machining program.
FIG. 4 illustrates an exemplary machining program that has been
inserted with a "look-ahead block supplement code". In the example
illustrated in FIG. 4, a code called "M400" is inserted into the
machining program as the "look-ahead block supplement code".
In the machining program, the "look-ahead block supplement code" is
inserted into a block at which a speed control abnormality is
likely to occur when the machining program is executed due to a
reduction in the look-ahead blocks.
When the "look-ahead block supplement code" is detected, the
operation limitation unit 116 compares the look-ahead blocks at
that time and the required look-ahead blocks and, if the look-ahead
blocks is less than the "required look-ahead blocks", the operation
limitation unit 116 limits execution of the machining program by
the program execution unit 111 until the look-ahead blocks looked
ahead by the program look-ahead unit 112 reaches the required
look-ahead blocks.
For example, the operation limitation unit 116 may reduce the
operation speed of the machine tool specified in the machining
program as a limitation on the execution of the machining
program.
With this configuration, the speed at which the program execution
unit. 111 executes the machining program slows down and, during
this time, the program look-ahead unit 112 continues to look ahead
at the machining program to thereby supplement the look-ahead
blocks.
FIG. 5 is a graph for showing difference in the look-ahead blocks
over time when the operation limitation unit 116 reduces the
operation speed of the machine tool.
Simultaneously with "No. 2", for example, when machining of the
second blade of the impeller 80 in FIG. 9 starts, the operation
speed of the machine tool 200 is reduced and the program look-ahead
unit 112 looks ahead at the machining program. As a result, the
look-ahead blocks increases and the graph shows growth.
After the look-ahead blocks reaches the required look-ahead blocks,
the machine tool operates at a normal operation speed. Therefore,
although the look-ahead blocks reduces, the look-ahead blocks does
not become zero.
Simultaneously with "No. 3", for example, when machining of the
third blade of the impeller 80 in FIG. 9 starts, the operation
speed of the machine tool 200 is reduced again and the program
look-ahead unit 112 looks ahead at the machining program. As a
result, the look-ahead blocks increases again and the graph shows
growth.
This increase and decrease in the look-ahead blocks repeats until
the machining ends.
Alternatively, the operation limitation unit 116 may instruct the
program execution unit 111 to stop executing the machining program
as a limitation on the execution of the machining program.
While the machining program is stopped, the program look-ahead unit
112 continues to look ahead at the machining program, to thereby
supplement the look-ahead blocks.
FIG. 6 is a graph for showing difference in the look-ahead blocks
over time when the operation limitation unit 116 instructs the
program execution unit 111 to stop executing the machining
program.
Simultaneously with "No. 2", for example, when machining of the
second blade of the impeller 80 in FIG. 9 starts, the program
look-ahead unit 112 looks ahead at the machining program while
execution of the machining is stopped. As a result, the look-ahead
blocks increases vertically. After the look-ahead blocks reaches
the required look-ahead blocks, the machine tool operates at a
normal operation speed. Therefore, although the look-ahead blocks
reduces, the look-ahead blocks does not become zero.
Simultaneously with "No. 3", for example, when machining of the
third blade of the impeller 60 in FIG. 9 starts, the program
look-ahead unit 112 looks ahead at the machining program while
execution of the machining is stopped. As a result, the look-ahead
blocks increases vertically. This increase and decrease in the
look-ahead blocks repeats until the machining ends.
Through configuring the numerical controller 100 in this way, the
operation speed of the machine tool is reduced and execution of the
machining program is stopped at a block at which a speed control
abnormality is expected to likely occur. During this time, the
numerical controller 100 continues to look ahead at the machining
program to supplement the look-ahead blocks. As a result, the
required look-ahead blocks can be secured and the possibility of a
speed control abnormality occurring can be reduced.
3. Operation of Invention
Now, operation of the numerical controller 100 according to the
first embodiment of the present invention is described with
reference to FIG. 7.
In Step S11, the program execution unit 111 executes a simulation
of the machining program.
In Step S12, in parallel with the machining program simulation
executed by the program execution unit 111, the program look-ahead
unit 112 looks ahead at the machining program before executing the
simulation.
In Step S13, the look-ahead blocks calculation unit 113 calculates
the look-ahead blocks.
In Step S14, if the look-ahead blocks falls below the required
look-ahead blocks (S14: YES), the processing moves to Step S15.
If the look-ahead blocks is more than or equal to the required
look-ahead blocks (S14: NO), the processing moves to Steps S11 and
S12.
In Step S15, the operation limitation unit 116 limits execution of
the machining program.
More specifically, the operation limitation unit 116 may be made to
reduce the operation speed of the machine tool 200 specified in the
machining program or may instruct the program execution unit 111 to
stop executing the machining program.
In Step S16, the look-ahead blocks is more than or equal to the
required look-ahead blocks (S16: YES), the processing moves to
Steps S11 and S12 (return). If the look-ahead blocks is less than
the required look-ahead blocks (S16: NO), the processing moves to
Step S15.
4. Effects of the Embodiment
The numerical controller 100 according to the embodiment of the
present invention includes the look-ahead blocks calculation unit
113 that calculates the look-ahead blocks, which is the difference
between a first sequence number that is the number of a block in
the machining program that is being executed and a second sequence
number that is the number of a block that is looked ahead, the
required look-ahead blocks setting unit 114 that sets a required
look-ahead blocks, which is the look-ahead blocks required for
executing the machining program, and the operation limitation unit
116 that compares the look-ahead blocks to the required look-ahead
blocks and, if the look-ahead blocks is less than the required
look-ahead blocks, limits execution of the machining program until
the look-ahead blocks reaches the required look-ahead blocks.
With this configuration, it is possible to detect the position in
the machining program at which a speed control abnormality is
likely to occur due to an insufficient look-ahead blocks that are
used to determine an acceleration/deceleration operation, and
supplement the look-ahead blocks at that position in order to
stabilize feed rate, cutting speed and other factors.
The numerical controller 100 also includes a storage unit that
stores blocks to be looked ahead, where the stored blocks are
consumed by executing the program. The required look-ahead blocks
setting unit 114 sets the required look-ahead blocks on the basis
of the maximum capacity of the storage unit.
As a result, the required look-ahead blocks can be set according to
the capacity of the storage unit (for example, a buffer) that
stores the look-ahead blocks, and the likelihood of the required
look-ahead blocks being incorrect can be reduced.
The numerical controller 100 also includes a memory that stores the
required look-ahead blocks, and the required look-ahead blocks
setting unit 114 uses the required look-ahead blocks stored in the
memory to set the required look-ahead blocks.
As a result, if, for example, a required look-ahead blocks needs to
be set for each of a plurality of machining programs, management of
the required look-ahead blocks can be made simple.
In the numerical controller 100, the required look-ahead blocks
setting unit 114 sets the required look-ahead blocks on the basis
of a variable that is written in the machining program together
with the look-ahead block supplement code.
Using a variable to set the required look-ahead blocks makes it
possible to freely change the required look-ahead blocks.
If the machining program contains an iteration of a code that
corresponds to identical machining, the number of consumed blocks,
which is the look-ahead blocks consumed when the code was
previously executed, is stored and, when the code is executed next
and for subsequent times, the required look-ahead blocks setting
unit 114 sets the required look-ahead blocks by adding the number
of consumed blocks to the look-ahead blocks before execution of the
code.
As a result, if the same machining needs to be iterated such as in
impeller machining, time-consuming procedures such as manually
inputting the required look-ahead blocks for each process of
machining can be avoided.
The operation limitation unit 116 reduces the operation speed of
the machine tool 200 specified in the machining program as a
limitation on the operation of the machine tool 200.
By reducing the operation speed of the machine tool 200 and having
the program look-ahead unit 112 look ahead at the machining program
while operation speed is reduced, it is possible to supplement the
look-ahead blocks.
The operation limitation unit 116 also instructs the program
execution unit 111 to stop executing the machining program as a
limitation on the operation of the machine tool 200.
Through stopping execution of the machining program and having the
program execution unit 112 look ahead at the machining program
while the machining program is stopped, it is possible to
supplement the look-ahead blocks.
5. Modification Examples
5.1 Modification Example 1
In the above-described example, the operation limitation unit 116
compares the look-ahead blocks to the required look-ahead blocks to
detect a block at which a speed control abnormality is likely to
occur, and supplements the look-ahead blocks at that block.
However, the operation limitation unit 116 is not limited to this
configuration.
For example, the operation limitation unit 116 may supplement the
look-ahead blocks when the rate of reduction of the look-ahead
blocks exceeds a prescribed value.
5.2 Modification Example 2
In the above-described embodiment, the look-ahead block supplement
code is inserted into the machining program, but the present
invention is not limited to this configuration. For example, the
numerical controller 100 may include a "supplement code addition
unit" that detects the position of an "exhaustion block" at which
the look-ahead blocks falls below a prescribed value when the first
simulation is executed, and that automatically inserts the
look-ahead block supplement code into the exhaustion block.
(In this embodiment, the "look-ahead block supplement code" that is
inserted by the supplement code addition unit is also referred to
as a "third code".)
An embodiment of the present invention has been described above,
but the present invention is not limited to the above-described
embodiment.
Any described effects are merely the best effects achieved by the
present invention and the effects achieved by the present invention
are not limited to the description provided herein.
The control method used by the numerical controller 100 is
implemented by software.
When using software, the programs that constitute said software are
installed on a computer (numerical controller 100).
These programs may be recorded on a removable medium and
distributed to a user or may be made available as a file to be
downloaded to a user's computer via a network.
These programs may also be provided to a user's computer (numerical
controller 100) as an Internet service via a network, instead of
being downloaded.
EXPLANATION OF REFERENCE NUMERALS
10 control system 100 numerical controller 111 program execution
unit 112 program look-ahead unit 113 look-ahead blocks calculation
unit 114 required look-ahead blocks setting unit 115 supplement
code detection unit 116 operation limitation unit 200 machine
tool
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